At present China's metallurgical industry, the high-pressure boiler pipe mainly used in the detection of 160 mm the following specifications, and most of the traditional eddy current through the coil or a separate sink ultrasonic detection methods. For more than 160 mm seamless steel pipe using the traditional method through the eddy current testing, there are many problems, but also the national standards allowed. If using an independent ultrasonic testing, ultrasonic testing mechanism exists because the surface of a certain depth of the blind, the overall test results can not guarantee the reliability of steel.
Through the coil eddy current probe is a circumferential surface of the pipe surface. Through the use of eddy current coils, the larger the diameter of pipe to be detected, detection of the circumferential area of the coil the greater, the lower signal to noise ratio. It is for this reason, pipe eddy current testing standards, the use of eddy current through the coil of its foreign economic size not greater than 140 mm. In addition, the large-diameter pipe through the type testing, the pipe magnetization and demagnetization and so there is a certain degree of difficulty.
Tank ultrasonic testing is used in the steel spiral forward type, ultrasound probe stationary. It was seized by the sink and the water pipe at the bottom of the full coupling characteristics, to ensure the thickness of the coupling constant. But because ultrasonic detection of internal defects on the surface of the main and sub-surface defects exist blind, preventing detection, coupled with spiral forward type, 12 m long pipe needs for space 30m venues such as inadequate pipe detection method has affected the selection and promotion.
Therefore, the domestic large-diameter steel pipe for testing, generally using magnetic flux leakage or water pressure test. In the country, there is no good performance for large diameter steel pipe magnetic flux leakage detection equipment produced, the use of which is imported. Imported magnetic flux leakage detection equipment is expensive, for the majority of domestic enterprises is difficult to accept; while the hydraulic test inefficient, labor-intensive, especially when the operator is not high sense of responsibility, the water pressure test useless. Visible to achieve large-diameter seamless steel pipe industry, metallurgical testing has become an urgent issue.
Is characterized by large-diameter steel pipe diameter, wall thickness is relatively thick, so take advantage of this feature based on ultrasound and eddy current testing internal surface and subsurface features combine to achieve "blind" testing. Through the use of "in situ pipe rotation detection probe forward combinations", not only to solve detection problems, but also to solve narrow space occupied space.
Monday, July 29, 2013
Welded steel pipe stress corrosion
Currently, the project is widely used welding cooling after annealing disposal to eliminate residual stress, residual stress after welding cooling is an important process of attack, this approach not only a waste of power and simple attack a larger weld residual stresses. Health Stress corrosion cracking is a necessary condition for coexistence of tensile stress and corrosive media, the tensile stress is an important condition for stress corrosion attack.
Stress corrosion of welded pipes in a particular environment as long as the attack ability, heat treatment after welding is a new skill to eliminate residual stresses. Preheated before welding to the data after heat treatment temperature and the welding process, welding pieces continue to insist that the heating temperature, the welding is completed using its thermal insulation cotton so slow cooling. Useful heat treatment after welding can weld residual stress decrease, and the heat treatment temperature is higher, the better to eliminate residual stresses. Post-weld heat treatment can also be useful for the progress of welded steel stress corrosion ability, after the heat treatment temperature is higher, resistance to stress corrosion ability and progress more obvious.
Stress corrosion cracking is a low-stress brittle cracking. Stress corrosion cracking is a petrochemical equipment, especially oil pipeline welded pipe and piling pipe common cause of failure. Stress corrosion cracking is a lag-related damage and the time, this and similar hydrogen delayed cracking completely. As long as there is stress, stress corrosion cracking attack abilities. Such stress can be applied so that the stress, or the process of welding and processing T residual stress introduced, the etching product may be a result of the expansion wedge effects of stress.
Stress corrosion of welded pipes in a particular environment as long as the attack ability, heat treatment after welding is a new skill to eliminate residual stresses. Preheated before welding to the data after heat treatment temperature and the welding process, welding pieces continue to insist that the heating temperature, the welding is completed using its thermal insulation cotton so slow cooling. Useful heat treatment after welding can weld residual stress decrease, and the heat treatment temperature is higher, the better to eliminate residual stresses. Post-weld heat treatment can also be useful for the progress of welded steel stress corrosion ability, after the heat treatment temperature is higher, resistance to stress corrosion ability and progress more obvious.
Stress corrosion cracking is a low-stress brittle cracking. Stress corrosion cracking is a petrochemical equipment, especially oil pipeline welded pipe and piling pipe common cause of failure. Stress corrosion cracking is a lag-related damage and the time, this and similar hydrogen delayed cracking completely. As long as there is stress, stress corrosion cracking attack abilities. Such stress can be applied so that the stress, or the process of welding and processing T residual stress introduced, the etching product may be a result of the expansion wedge effects of stress.
Widely uses of thermal expansion straight seam steel pipe
thermal expansion of straight seam steel pipe has a range of models, which can be expanded from what to what model are fixed, straight seam steel pipe model and the target model itself to be close to, or pipe break. He is given by high-frequency straight seam steel pipe body hardness decreased heating so then let straight seam steel pipe from the header (header is mold, a narrow one wide, narrow tube is a normal caliber, the thickest section of the target diameter) By slowly on, when the tube completely through after reaching thermal expansion purposes.
Thermal expansion process on the straight seam steel pipe and weld material itself has a high demand, the material must meet the national standard, the carbon content must not be less, or will cause tube breakage, another seam have qualified, or in the process of thermal expansion very easy to disconnect. Thermal expansion is a certain risk. Care workers sometimes the case during thermal expansion rate is not well controlled, and other factors, it is easy to break the tube. After thermal expansion after the pipe, there will be a certain length and thickness shrunk, so in the process of purchasing the original tube, try to buy some little thicker wall thickness, and length slightly longer, so as to ensure that the thermal expansion of the walls after thickness and length to achieve the project's requirements. Generally straight seam steel pipe thermal expansion for steel.
Straight seam steel pipes are widely used, including water and structure of urban construction and other fields. During use, straight seam steel pipes some general models: can not meet the needs of the project, this time straight seam steel pipe thermal expansion to play a big role, thermal expansion is straight seam steel pipe after treatment by thermal expansion of straight seam steel pipe.
Thermal expansion process on the straight seam steel pipe and weld material itself has a high demand, the material must meet the national standard, the carbon content must not be less, or will cause tube breakage, another seam have qualified, or in the process of thermal expansion very easy to disconnect. Thermal expansion is a certain risk. Care workers sometimes the case during thermal expansion rate is not well controlled, and other factors, it is easy to break the tube. After thermal expansion after the pipe, there will be a certain length and thickness shrunk, so in the process of purchasing the original tube, try to buy some little thicker wall thickness, and length slightly longer, so as to ensure that the thermal expansion of the walls after thickness and length to achieve the project's requirements. Generally straight seam steel pipe thermal expansion for steel.
Straight seam steel pipes are widely used, including water and structure of urban construction and other fields. During use, straight seam steel pipes some general models: can not meet the needs of the project, this time straight seam steel pipe thermal expansion to play a big role, thermal expansion is straight seam steel pipe after treatment by thermal expansion of straight seam steel pipe.
Sunday, July 28, 2013
The importance of seamless welding defect detection
Seamless hollow sections, a large number of channels for transporting fluids, such as the transportation of oil, natural gas, coal gas, water and some solid materials, pipes and so on. Steel pipe and solid steel bar, etc. compared to the same torsional strength in bending, lighter, is an economic cross-section steel, widely used in the manufacture of structural parts and mechanical parts, such as piling pipe, automotive drive shafts, bicycle rack and construction using steel scaffolding.
In addition, with the Beijing seamless manufacturing annular parts, can improve material utilization, simplify the manufacturing process, saving material and machining time, such as bearing rings, jack sets, has been widely used to make steel. Steel or a variety of conventional weapons indispensable material, barrel, barrel, etc. to make steel. By cross-sectional shape of the pipe can be divided into tube and shaped tubes. Since the perimeter of equal conditions, the maximum area of a circle with a circular tube can carry more fluid.
Magnetic particle testing or penetrant testing can effectively find seamless surface cracks, folds, double skin, hairline, pinholes and other surface defects. For ferromagnetic materials, magnetic particle inspection method should be preferred, because of its high detection sensitivity; For non-ferromagnetic material, such as stainless steel seamless pipe, then a penetration assay.
Reserved resection margin when both ends is small, causes the detection apparatus, both ends of the head may not be effectively detected, and ends there is most likely the site of cracks or other defects. If there is a potential end tendency to crack, the installation of the weld heat affected also possible to make the potential crack. Therefore, it should be noted that certain areas of the welded tube detection, to detect defects in steel tip extensions.
In addition, with the Beijing seamless manufacturing annular parts, can improve material utilization, simplify the manufacturing process, saving material and machining time, such as bearing rings, jack sets, has been widely used to make steel. Steel or a variety of conventional weapons indispensable material, barrel, barrel, etc. to make steel. By cross-sectional shape of the pipe can be divided into tube and shaped tubes. Since the perimeter of equal conditions, the maximum area of a circle with a circular tube can carry more fluid.
Magnetic particle testing or penetrant testing can effectively find seamless surface cracks, folds, double skin, hairline, pinholes and other surface defects. For ferromagnetic materials, magnetic particle inspection method should be preferred, because of its high detection sensitivity; For non-ferromagnetic material, such as stainless steel seamless pipe, then a penetration assay.
Reserved resection margin when both ends is small, causes the detection apparatus, both ends of the head may not be effectively detected, and ends there is most likely the site of cracks or other defects. If there is a potential end tendency to crack, the installation of the weld heat affected also possible to make the potential crack. Therefore, it should be noted that certain areas of the welded tube detection, to detect defects in steel tip extensions.
Friday, July 26, 2013
Post weld heat treatment on the stress corrosion resistance welded steel pipe impact
Welded steel pipe stress corrosion only in certain circumstances take place, it also has some of the following characteristics: (a) only if there is stress (especially tensile stress) only when the stress corrosion cracking. This stress can be applied stress, T or introduced during welding and processing the residual stress corrosion products can also be caused by the action of the expansion wedge stress. (2) Stress corrosion cracking is a lag time-related damage, which is completely similar to delayed cracking and hydrogen. (3) Stress corrosion cracking is a low-stress brittle fracture.Stress corrosion cracking is a petrochemical equipment, especially oil pipeline - a common cause of failure of welded tube. Due to stress corrosion cracking occurred unpredictability, so the petrochemical industry, the biggest hidden dangers. Stress corrosion cracking is a necessary condition for coexistence of tensile stress and corrosive media, the tensile stress is an important condition for stress corrosion. In the petrochemical and nuclear industries such as equipment, most of the stress caused by stress
Corrosion cracking is caused by the residual tensile stress, it is often superimposed on stress at work. Mainly from the device residual stresses produced during the welding residual stresses. Currently, the project is widely used welding cooling after annealing treatment to eliminate residual stress, while cooling after welding residual stress is an important process, this approach is not only a waste of energy and easy to produce larger welding residual stresses. Heat treatment after welding is a new technique to eliminate the residual stress. Preheated before welding the material to a heat treatment temperature after the welding process and welding pieces of heating was continued to maintain this temperature, the soldering is completed using heat insulation cotton to its slow cooling. This method can effectively reduce residual stress and improve the stress corrosion resistance of metals.
Heat treatment after welding can reduce the residual stress, and heat treatment temperature is higher, the better to eliminate the residual stress. PWHT welded steel pipe can effectively improve the resistance to stress corrosion, after the heat treatment temperature is higher, increasing resistance to stress corrosion is more significant.
Corrosion cracking is caused by the residual tensile stress, it is often superimposed on stress at work. Mainly from the device residual stresses produced during the welding residual stresses. Currently, the project is widely used welding cooling after annealing treatment to eliminate residual stress, while cooling after welding residual stress is an important process, this approach is not only a waste of energy and easy to produce larger welding residual stresses. Heat treatment after welding is a new technique to eliminate the residual stress. Preheated before welding the material to a heat treatment temperature after the welding process and welding pieces of heating was continued to maintain this temperature, the soldering is completed using heat insulation cotton to its slow cooling. This method can effectively reduce residual stress and improve the stress corrosion resistance of metals.
Heat treatment after welding can reduce the residual stress, and heat treatment temperature is higher, the better to eliminate the residual stress. PWHT welded steel pipe can effectively improve the resistance to stress corrosion, after the heat treatment temperature is higher, increasing resistance to stress corrosion is more significant.
Large diameter spiral steel pipe for liquid transfer applications with a range
Spiral steel pipe manufacturing method into their large diameter spiral steel pipe and spiral steel two kinds. Spiral welded pipe with high-quality carbon steel or alloy steel, hot-rolled, cold-rolled (pull) of the points. Large diameter spiral pipe is rolled into a tube-shaped steel plates on the seam or spiral seam welded together, in the manufacturing method, is divided into low pressure liquid delivery welded steel pipe, spiral welded steel pipe, straight welded steel pipe, welded pipe, etc. . Spiral welded pipe can be used for a variety of liquids, gas pipelines and so on. Welded pipes can be used for water pipes, gas pipes, heating pipes.
Large diameter spiral steel pipe is the industrial, construction and other industries widely used kind of steel. It is a strip coil as raw material, often warm extrusion molding, with automatic double-sided submerged arc welding process wire spiral welded steel pipe. Mainly used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction.
Large diameter spiral steel pipe for the transport of liquids: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe for bridges; docks, roads, buildings and other structures tube. It is in the transportation of gas, transportation has played a significant role. Large diameter spiral pipe pressure transmission fluid with spiral submerged arc welded pipe is mainly used to transport oil, natural gas pipelines; pressure transmission fluid with frequency spiral welded steel pipes, lap welding method with high frequency welding for Order pressure fluid transfer frequency spiral welded steel pipe. Strong pressure steel, plastic, and easy welding and machining molding; generally low pressure liquid delivery spiral submerged arc welded pipe, using double-sided automatic submerged arc welding or welding into the legal system for water, gas, air and steam low pressure liquid delivery SAW pipe.
Large diameter spiral steel pipe is the industrial, construction and other industries widely used kind of steel. It is a strip coil as raw material, often warm extrusion molding, with automatic double-sided submerged arc welding process wire spiral welded steel pipe. Mainly used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction.
Large diameter spiral steel pipe for the transport of liquids: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe for bridges; docks, roads, buildings and other structures tube. It is in the transportation of gas, transportation has played a significant role. Large diameter spiral pipe pressure transmission fluid with spiral submerged arc welded pipe is mainly used to transport oil, natural gas pipelines; pressure transmission fluid with frequency spiral welded steel pipes, lap welding method with high frequency welding for Order pressure fluid transfer frequency spiral welded steel pipe. Strong pressure steel, plastic, and easy welding and machining molding; generally low pressure liquid delivery spiral submerged arc welded pipe, using double-sided automatic submerged arc welding or welding into the legal system for water, gas, air and steam low pressure liquid delivery SAW pipe.
High-frequency welded pipe welding speed and performance of rust
In general, high-frequency welded pipe during welding, the welding quality and welding speed are related. As the heating time can be shortened, the time the metal oxide shortened, therefore, the quality of the welding speed and the welding speed with increased.
If the welding speed is reduced, so that the heating zone will not only wider, but also with the molten zone width and change the heat input and thus the formation of burrs is large, so the high-frequency welded pipe, the welding equipment and the unit should be means the maximum allowable speed according to different specifications and varieties select the appropriate welding speed.
In order to achieve high-frequency welded pipe rust the desired effect, according to the choice of materials abrasive surface hardness and high frequency welded pipe extent of corrosion, surface roughness, for reasonable operation. Meanwhile, in order to achieve the desired effect of rust, for single-layer epoxy, two or three layers polyethylene coating should be mixed abrasive grit and steel shot to operate.
If the welding speed is reduced, so that the heating zone will not only wider, but also with the molten zone width and change the heat input and thus the formation of burrs is large, so the high-frequency welded pipe, the welding equipment and the unit should be means the maximum allowable speed according to different specifications and varieties select the appropriate welding speed.
In order to achieve high-frequency welded pipe rust the desired effect, according to the choice of materials abrasive surface hardness and high frequency welded pipe extent of corrosion, surface roughness, for reasonable operation. Meanwhile, in order to achieve the desired effect of rust, for single-layer epoxy, two or three layers polyethylene coating should be mixed abrasive grit and steel shot to operate.
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